Known switching devices used in electrical circuits, such as in low or medium voltage electric circuits, such as circuit breakers, disconnectors and contactors, are devices designed to allow the correct operation of specific parts of the electric circuits in which they are installed, and of the associated electric loads. In the context of the present disclosure, the term “low voltage” is referred to applications with operating voltages up to 1000V AC/1500V DC, and the term “medium voltage” is referred to applications in the range from 1 kV to some tens of kilovolt, e.g. 50 kV.
Switching devices can be actuated during their operation from an open position to a closed position to allow a current flowing therethrough and from the closed position to the open position to interrupt such current flowing.
The switching devices include one or more electrical poles, or phases, each having at least a contact movable between a first position, or coupled position, in which it is coupled to a corresponding fixed contact (e.g., switching device in the closed position), and a second position, or separated position, in which it is spaced away from the corresponding fixed contact (e.g., switching device in the open position).
A suitable operating mechanism is operatively associated to the movable contacts to cause the displacement of such movable contacts between the coupled and separated positions.
Coil-based actuators, hereinafter indicated as “coil actuators”, are frequently used in switching devices, for example in mechanical operated switching devices for low or medium voltage circuits; mechanically operated switching have an operating mechanism of the known “stored-energy” type, wherein the energy specified for opening the switching device is stored in suitable elastic means, such as springs.
A coil actuator can be used to release mechanical parts of the associated switching device, e.g. corresponding parts of the operating mechanism, so as to open or close the switching device itself, following an opening or a closure command and/or event. Examples of such coil actuators are opening shunt releases, closure shunt releases or undervoltage shunt releases, which are all devices known in the art.
A timing test diagnostic function is requested for evaluating the reliability of the switching device. The timing test diagnostic function measures the time elapsed during the opening operation and/or the closure operation of the switching device.
In known implementations, the timing test diagnostic function is performed by means of various additional equipment which are operatively connected to the switching device and which use the information on the position of the movable contacts, information that is provided for instance by suitable auxiliary contacts.
The additional equipment can include for example: portable instruments for service tasks, IEDs (“intelligent electronic devices”) with advanced diagnostic functionalities, electronic protection relays, diagnostic and/or monitoring instruments. The use of such external equipment implies a series of disadvantages, among which: complex wiring and cabling, high installation costs, and encumbrance due to the large volume occupied by the additional equipment.
Therefore, while the known implementations perform satisfactorily, further improvements to this technology are still desired.